Do I Need “Ditra” Under Floor Tiles?

in How Do I ...

schluter-ditra section view I just read a discussion thread on the Canadian Woodworking forum where the question asked was:

"Ditra for kitchen flooring – Is it worth it?”

I discovered this product last year while researching methods for laying a ceramic tile floor for an upstairs bathroom renovation in our old farmhouse.

 

What the heck is Ditra?

The short answer is that it’s an underlayment used under tile and stone flooring to "decouple" the ceramic tiles from the subflooring, which may be subject to expansion or deflection which can cause tiles or grout lines to crack.

The practice of decoupling has been performed for thousands of years by using a layer of sand under stone floors. Ditra was invented by Schluter-Systems back in 1987 and is used extensively in commercial and residential tile installations.

Ditra installation video:

 

But it’s expensive!

Yes it is. But if it prevents your floor from failing after a few years then it’s probably worth it.

There was an alternative product mentioned in the forum thread called "Protegga" which looks to be a slightly less expensive copy of the Ditra (you can read John Bridge’s comments about Ditra knockoffs on his tile forum).

The price difference between the two products here in Canada is currently about 33 cents per sq ft, so the Protegga would cost $50.00 less for 150 sq ft.

 

I went with the Ditra

After reviewing the alternatives on forums and reading the product data sheets, I decided Ditra was the safest bet for my situation. I was tiling over a vinyl composite tile that was in good condition and didn’t want to raise the floor any higher than necessary.

The product comes in a roll, so it was a lot easier to deal with in a small space than trying lay a plywood subfloor.

laying tile over ditra in bathroom laying ditra over composite tile floor

 

Thinset mortar

One thing you’ll need to pay attention to is using the proper type of thinset mortar:

For installing the Ditra membrane:

  • over plywood or OSB – use MODIFIED Thinset mortar.
  • over concrete or gypsum – use UNMODIFIED Thinset mortar

For installing tiles on Ditra:

  • use UNMODIFIED Thinset mortar

(learn about Modified vs Unmodified (dryset) thinset here)

 

Fourteen months later, everything looks good so far. If I find myself needing to tile over anything other than new, level concrete, I’ll probably go with Ditra again.

 

 

If you don’t want to miss a tip, and aren’t already signed up for our Stonehaven Life updates by email, you can subscribe right here, right now.

 

  

{ 1 comment… read it below or add one }

Sherwood

For what it’s worth (not much) I laid 1 foot tiles in our laundry room, adding 3/4″ floor grade OSB over the existing subfloor, then priming it with latex primer to protect the wood from the morter. It’s been in place now for 5 years with no cracks.

This is probably the luck of the draw. I could probably do this, and 9/10 of the time it would work. A pro can’t afford 10% failures.

Much of the issue to me is the nature of tile, and the nature of adhesive. You’re using materials that are intrinsically brittle. The right adhesive combined with a stronger tile should make decoupling membranes unnecessary. The right adhesive might be one that would slowly deform under stress, reaching a new accomodation.

Leave a Comment

Previous post:

Next post: